In the Feb. 16 SN: Robots roll into the classroom, brain zaps for severe depression, particle colliders of the future, how to walk like a tetrapod, sleepless nights boost Alzheimer's proteins and more.

Making waves

Locked in a deadly embrace, two white dwarf stars may be the strongest source of gravitational waves now flooding our galaxy. The stars appear to be separated by just one-fifth the Earth-moon distance.

New X-ray observations of the duo, which resides roughly 1,600 light-years from Earth, indicate that the dwarfs take just under 5.5 minutes to orbit each other and are the most-compact binary-star system known. NASA's Chandra X-ray Observatory also found that the pair's orbital period is declining by 1.2 milliseconds each year.

According to Einstein's theory of gravitation, the white dwarfs are spiraling toward each other because they're losing energy in the form of

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